1. Field of the Invention
The present invention relates to an activation control apparatus for a power generation plant including a steam turbine.
2. Description of the Related Art
In a power generation plant which uses renewable energy as represented by wind-power generation or photovoltaic power generation, the power generation amount obtained by renewable energy varies significantly depending upon the season, the weather or the like. Therefore, for a steam turbine provided in a power generation plant of the type described, reduction of activation time (high-speed activation) is demanded in order to stabilize the system power.
Since, in activation of a steam turbine, the temperature and the flow rate of steam which flows into the steam turbine increase rapidly, the temperature of the surface of a turbine rotor increases rapidly in comparison with that of the inside. As a result, the stress (thermal stress) arising from a temperature difference between the surface and the inside of the turbine rotor increases. Since excessive thermal stress may reduce the lifespan of the turbine rotor, upon activation of the steam turbine, it is necessary to control the input heat amount to the steam turbine such that the increased thermal stress may remain within a range of a limit value determined in advance. Further, upon activation of the steam turbine, the turbine rotor and a casing which accommodates the turbine rotor therein are exposed to and heated by high-temperature steam. Therefore, they are extended particularly in an axial direction of the turbine by thermal expansion (thermal extension). Since not only the structure but also the heat capacity are different between the turbine rotor and the casing, the thermal extension of the turbine rotor and the thermal extension of the casing become different from each other (thermal extension difference). If the thermal extension difference increases, then there is the possibility that the turbine rotor that is a rotary member and the casing that is a static body may be contacted with and damaged by each other. Therefore, it is necessary to control the input heat amount to the steam turbine such that the thermal extension difference may remain within a range of a limit value determined in advance. In this manner, since several constraint conditions to be taken into consideration are involved in activation of the steam turbine, it is necessary to perform activation control such that such constraint conditions are satisfied.
As an activation control method of the type described, a method is available in which, before starting of activation, a predetermined set of activation sequences each configured from a plurality of setting points is selected based on an activation mode and activation control of a steam turbine is performed from a setting point to a different setting point in accordance with the selected activation sequence (refer to JP-2013-144982-A and so forth).